Electroplating apparatus



Nov. 8, 1949 A. E. THURBER ELECTROPLATING APPARATUS Filed Sept. 29, 1945 E M l 1 Patented Nov. 8, 1949 1' g 2,487,399 I UNITED STATES PATENT OFFICE ELECTROPLATING APPARATUS Arthur E. Thurber, Sheri-ill, N. Y., asslgnor to Oneida Ltd, Oneida, N. 1., a corporation New York Application September 29, 1943, Serial No. 504,220 2 Claims. (Cl. eon-264) l 2 This invention relates to electroplating. following description, however, the invention is It is an object of the invention to provide an equally applicable to plating generally, requiring improved purifying system for electroplating only suitable modification in the shape of the apparatus. tank'and its component elements for dealing with It is a further object of the invention to proarticles and anodes of various shapes.

vide an improved circulating and filtering system The plating tank, which is designated generally by means of which the harmful effects of anodic by the numeral 1, is divided by a porous partlparticles on the deposit may be eliminated. tion or membrane 2 into an anodic cell 3, enclosed The harmful effects Of pe Solids, s h within the membrane and a cathodic cell 4 outas anodic particles, upon electroplating havelong side the membrane and surrounding the anodlc en recognized n it ha been proposed to cell. An outlet connection 5 leads out of the tank remedy this condition by continuous or intermiti from the bottom of the anodic cell 3 and an tent filtration or by the use of bags surrounding inlet connection 6 leads into the tank adjacent the anodes. the top of the cathodic cell 4. An anode 1 is Where bags are used the electrolyte within 5 placed within the anodic cell 3 and the cathodes. the bag becomes very high in dissolved metal'and or articles to be plated, v8, are placed within the low in the chemicals which are required for-good cathodic cell 4. anode corrosion, thus interfering with the proper By means of the circulating system, described plating action. In addition, all the various im-. more fully below, the electrolyte is pumped into purities whether in solution or in colloidal or the tank I through the inlet 6 to a level slightly solid suspension, build up concentration within above the partition wall or membrane 2 so that it the bag and then seep through and contaminate continuously overflows from the top of the the entire electrolyte, resulting in inefficiency and cathodic cell into the anodic cell. Electrolyte is p quality depositscontinuously withdrawn through the outlet 5 Ordi ary fil procedures likewise fall short from the anodic cell so as to maintain a. suitable of the intended purpose. Continuous filtration, level therein, as indicated by the numeral 9, thus as heretofore practiced, never completely removes maintaining a continuous circulation, and the particles from the electrolyte and due to the further, where desired, maintaining a slightly disturbance a s y he fi rin Circulation, lower hydrostatic pressure within the anodic cell may st p particles which would otherwise so as to produce a tendency for electrolyte to settle out and thus produce a condition which is flow from the cathodic cell into the anodic cell, worse than where no filtering is e p ye rather than reversely. termittent filtration, as where the entire electro- The circulating system associated with the lyte is removed and is returned after filtration, mating tank 1 comprises a line containing a obviously causes undesirable interruptions in the :35 valve H, which passes from the outlet 5 to the plating operation and can produce a really clean bott of a verfl tank 12. Th overflow of electrolyte only immediately after the filtering the tank I2 is arranged So as to maintain electrohas been done, so that after a very short time the lyte therein at the level 9, previously mentioned, anode particles will have formed and the bath will in this way controlling the electrolyte level withno longer be free of such particles. n in the anodic cell 3. Tank 12 discharges in turn According to the present invention, a novel through a line l3 into a storage tank or reservoir form of circulation is employed, the plating tank II from which the electrolyte is withdrawn being divided into an anodic cell and a cathodic through an outlet I5 by a pumping and filtering cell separated by a porous membrane or partition unit Hi from which it is delivered through the and a continuous circulation between the anodic 5 line 11 toward the bottom of a second overflow cell and a filtering system is provided, so that the tank I8. The tank 18 communicates through an electrolyte within the anodic cell is kept in the outlet I9 and valve 20 with the inlet 6 of the platmost desirable condition at all times, while no in; tank I and in this way the level 2!, within the electrolyte is introduced into the cathodic cell cathodic cell 6 is maintained, being substantially until atter it has been filtered. the same level 2| as exists in the overflow tank 18,

The invention also contemplates the provision Tank has an overflow 22.. preferably positioned of a convenient and efliclent circulating and filterat a slightly higher level than the outlet 19, and ing system in conjunction with such a plating which communicates through the line 23 with the tank, by means of which the desired now relafiltration reservoir l4, previously referred to, and

tions are, readily maintained, serves to maintain the desired level of electro- The drawing illustrates schematically an aplyte within the tank 18.

paratus embodying, in a preferred form, the in- As will be observed, the line I5, pumping and vention and shows by way of example a form of filtering unit It, line H, tank l8, overflow 22, line apparatus which has been employed in silver 23 and reservoir l4 constitute a bypass through plating bearings. As will be understood from the which electrolyte may be pumped. continuously and at varying rates without affecting the amount or regularity of circulation of electrolyte through the tank I. The circulation through this bypass system may be gauged and controlled according to a pressure gauge 24 associated with the pumping and filtering unit [6.

In this way the filtering action may be con- While but a single plating tank I has been shown in association with the circulating system, a plurality of tanks may be connected through suitable manifolds with the overflow tanks 18 and 12, the action in all tanks being similar and in this case it is necessary only to provide piping in the circulating system which is of adequate diameter to take care of the increased amount of circulation required for a larger number of lating tanks.

The circulation within the plating tank itself is uniformly from the cathodic cell to the anodic cell so that no anode particles can pass intothe cathodic cell. The cathodic cell is supplied at all times with filtered electrolyte from the tank 18, and so also is the anodic cell so that no opportunity is given for the building up of suspended particles within the anodic cell. Where desired, the anode 1 may be rotated so as to provide for agitation to obtain greater anode corrosion. By placing a screen at the bottom of the porous membrane 2, shot anodes may be used. Agitation may be applied to the desired.

The separating wall or membrane 2 dividing the cathodic and anodic cells may be made of any suitable material which possesses the desired in operation, the circulation through the line 19 will also be constant, the heat exchanger may conveniently be locatedat'either of these points so as to deliver the electrolyte at the desired temperature directly to the plating tanks. While the invention has been shown as applied merely to thodic cell, an anodic cell, a porous membrane cathode 8 also, where characteristics of non-conductivity, a sufficiently fine structure to prevent assage of anodic particles and suflicient porosity to allow sufficient flow of electric current. Such materials as cloth, paper, ceramics or plastics are suitable and the specific material employed will of course depend upon the specific plating being done. In silver plating on bearings, with the usual cyanide electrolyte solution, either a membrane of cloth supported by a non-electrical framework or ceramic materials have been found suitable. A compose ite membrane formed :by placing finely divided material, such as diatomaceous earth between two layers of cloth or the like may'also be em-' ployed.

The circulating, system in addition to providing for filtration permits also convenient analysis and maintenance of the bath, as the bath may be tested and adjusted within the storage tank l4.

Likewise, where temperature control is of importance and where, as is usual, the room temperature is fairly stable, the temperature of the entire electrolyte may readily be maintained at the desired value by placing a heat exchanger at any point in the circulating line. Inasmuch as the circulation through the inlet 6 will be constant and with a given number of plating tanks separating the "said" cells, means for circulating electrolyte to and from said anodic cell and puri fying the same during such circulation, comprising an outlet connection from the bottom of the said anodic cell and a first tank for receiving electrolyte from said anodic cell and having an overflow to maintain the level in said tank and said anodic cell below the top of said membrane, a second tank for discharging electrolyte into said cathodic cell and having an overflow to maintain the level in said second tank and cathodic cell above the top of said membrane for causing overflow from said cathodic cell into said anodic cell, and means for maintaining a flow of electrolyte from said first tank to said second tank.

2. Electroplating apparatus comprising a cathodic cell, an anodic cell, a porous membrane separating the said cells, means for circulating electrolyte to and from said anodic cell and purifying the same during such circulation, comprising an outlet connection from the bottom of the said anodic cell and a first tank for receiving electrolyte from said anodic cell and having an overflow to maintain the level in said tank and said anodic cell below the top of said membrane, a second tank for discharging electrolyte into said cathodic cell and having an overflow to maintain the level in said second tank and cathodic cell above the top of said membrane, a storage tank for receiving electrolyte from said overflows and means for withdrawing electrolyte from said storage tank, filtering the same and discharging the filtered electrolyte into the said second tank.

ARTHUR E. THURBER.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 512,266 Andreoli Jan. 9, 1894 686,395 Dessolle Nov. 12, 1901 814,864 McDonald Mar. 13, 1906 871,161 Chaplin Nov. 19, 1907 874,064 Gibbs Dec. 17, 1907 961,945 Finlay June 21, 1910 1,371,699 Linder Mar. 15, 1921 1,395,827 Hybinette Nov. 1, 1921 1,587,438 Tainton June 1, 1926 1,945,107 Cain Jan. 30, 1934 1,980,381 Cain Nov. 13, 1934 2,014,148 Sievert Sept. 10, 1935 2,288,503 Weaver June 30, 1942 FOREIGN PATENTS Number Country Date Australia Aug. 30, 1929 

